Double-glazed or other sandwich type insulated windows are made by applying a spacer material to the periphery of a first glass lite and then applying a second glass lite over the spacer. A desiccant in the spacer serves to absorb any moisture in the trapped air. In order for a window to maintain its integrity, the seal between the glass lites must prevent any further moist air from entering the insulating space. The seal is established by the spacer which is adhesive on opposite edges, and later by a further application of sealant.
The spacer serves to maintain the separation between the glass lites in which the insulating air space is trapped. The spacer generally includes materials such as butyl polymers, silicones, polyvinyl polymers as well as strip metal and other materials. Commonly a strip of flexible insulating material of a cellular or solid structure, such as butyl rubber or silicone foam, is used which includes an impregnated desiccant, a polyester, e.g. MYLAR.TM., vapour barrier, and pressure sensitive adhesive on opposite edges for sealing to the glass. These spacer materials have an elastic memory and therefore stresses such as being wound around the delivery spool, or bent around curves or corners stretch the spacer unevenly resulting in the spacer trying to return to its natural position after it has been applied.
At present, most double glazed windows are formed by manually applying a length of spacer material about the periphery of the glass. Various types of manual tools are known for this purpose, requiring the operator to move the tool along the sides and ends of the glass lite while feeding a length of the strip or spacer material through or around the tool.
Typical of the arrangements known in the prior art is the device shown in U.S. Pat. No. 4,756,789, issued to Kolff, Jul. 12, 1988. The device provides a plurality of rollers between which is fed spacer material. A guide is provided on the body of the applicator for evenly measuring the spacing around the periphery of the substrate as the spacer is applied. Although a useful arrangement for limited production, this apparatus would be ineffective in an environment where high volume production is required.
As the insulated window industry has developed and improved, consumer tolerance for irregularities in window construction has diminished. The flexible spacer materials bend poorly around corners causing a visible bulge in the interior of the window. Commonly the practice for forming corners is to lift the applicator tool, bend the spacer material, replace the applicator tool and continue to apply spacer. In addition to forming a poor rounded corner, this practice also risks forming an incomplete seal with the glass in the corner areas where the tool is lifted and the adhesive is not pressed against the substrate by the tool. As discussed above, a complete seal is necessary to forming an insulating window. If the seal is broken or incomplete much of the insulating capacity of the window is lost and the glass becomes obscured by condensation.
Gradually the industry has turned to automation in insulated window production in order to increase the speed of production and uniformity of the product, and to reduce production costs. Briefly, the line process for automated or semi-automated window assembly includes a number of station steps. First the glass is washed; it is then fed through an aligning process to the spacer applicator; spacer is applied to the periphery of the glass; a glass lite with spacer applied is aligned with a second clean lite for sandwich assembly; the assembly is then advanced through a pressing roller; the edges are sealed; and the unit is placed in a frame. In an automated process it is important to limit the time in each station because all units advance at the rate of the slowest station. Once each station is occupied, a complete unit is produced from the line, for example, every 20 seconds, or a period equivalent to the duration of the longest station.
An apparatus for a partially automated system which has been proposed in the art for applying an adhesive spacer material to a substrate is disclosed in Lisec, U.S. Pat. No. 4,769,105, issued Sep. 6, 1988. The Lisec apparatus provides a spacer application head which is movable vertically on a carriage member. The glass to which the spacer is applied is movable on a pair of cooperating conveyors in a horizontal direction. In operation the head travels up one end of the glass, the glass is advanced while the head continues to apply spacer, the head travels down the other end, and the glass is returned in the horizontal direction to apply spacer to the fourth side. Thus the head travels the complete periphery of the glass and the operation finishes with the glass in its original starting position. This movement of the glass forward and back is time consuming. At each corner the feed of spacer material is held by a single gripper and the head is rotated. As a result the spacer material is bent, but no means is provided to ensure placement of the corner nor to ensure a good seal in the corner area. Although this patent recognizes the need for sharp corners, those formed by this apparatus still bulge, as is found with the hand applicator. Further, the Lisec device subjects the spacer material to significant stresses of bending and twisting which will deform the spacer making a square, even application impossible. The arrangement is likely more efficient than a hand-held apparatus. However, there is still a need for an apparatus to automatically apply spacer to a glass lite in window assembly with greater efficiency, and in particular to form better corners.
With the present invention, applicant has developed a method and apparatus for automated application of spacer material to substrates, especially glass. More particularly, the method and apparatus of this present invention are intended to automatically apply spacer material to glass lite assemblies suitable for in-line production.
Advantageously, the present method and apparatus provide the mechanism and steps necessary to produce tight accurate corners, including a punch for notching the spacer material in the corner area, and a cooperating pair of lead and lag grippers for forming accurate fold placement.
Furthermore, the present method and apparatus according to the present invention permit the fabrication of a high volume of insulated glass assemblies with a low level of manual intervention and skill required to operate the apparatus. As a result, an improved product is produced at greater cost efficiency with less safety risk to operators.